Semiconductor memory devices (resistance-change memories) configured to store data utilizing changes in the resistance of each memory element include a magnetic random access memory (MRAM), a resistive random access memory (ReRAM), and a phase-change random access memory (PCRAM).
The resistance-change memory is characterized in that a plurality of resistance states of a variable-resistance element are associated with data. For example, a low-resistance state of the variable-resistance element is defined to be binary 0. A high-resistance state of the variable-resistance element is defined to be binary 1.
Data is read from an MRAM by using a sense amplifier to compare a read current flowing through a memory cell with a reference current flowing through a reference cell. At this time, a read voltage is applied to the memory cell, and a reference voltage is applied to the reference cell. This method is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-297072.